Parent controls for children, name-tile sign-in, restricted Learn search, simple mode

- Sign-in page shows name tiles on remembered devices; tap a name, then PIN or passkey
- Music and Movies are separate on the server; Plex can be locked to a child's managed profile
- Activity log, weekly summary and alerts to parents; per-area and weekend limits
- Requests from children (Ask button) answered in Settings; bonus screen time from rewards
- Restricted Learn search (Simple English Wikipedia, blocked words) replaces web search for children
- Simple mode (big-button home) for young children or grandparents
- Child usage kept in memory instead of read from disk on every request
- Tests and README updated

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

push.js

@@ -47,8 +47,10 @@ async function send(dir, st, uid, payload) {
 }
 
 let lastEvents = 0;
+let lastDigest = 0;
 /** One pass over everyone: runs every minute. */
 async function tick(now = new Date(), force = false) {
+  if (now.getTime() - lastDigest >= 10 * 60e3) { lastDigest = now.getTime(); try { require('./activity').weeklyDigest(now); } catch (e) { console.warn('[push] weekly summary failed:', e.message); } } // (each child's week, to the parents, on Monday morning)
   const checkEvents = force || now.getTime() - lastEvents >= 4.5 * 60e3;
   if (checkEvents) lastEvents = now.getTime();
   for (const u of users.all()) {